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use std::time::Duration;
use crate::application::ApplicationHandler;
use crate::event::Event;
use crate::event_loop::{self, ActiveEventLoop, EventLoop};
/// Additional methods on [`EventLoop`] for pumping events within an external event loop
pub trait EventLoopExtPumpEvents {
/// A type provided by the user that can be passed through [`Event::UserEvent`].
type UserEvent: 'static;
/// Pump the `EventLoop` to check for and dispatch pending events.
///
/// This API is designed to enable applications to integrate Winit into an
/// external event loop, for platforms that can support this.
///
/// The given `timeout` limits how long it may block waiting for new events.
///
/// Passing a `timeout` of `Some(Duration::ZERO)` would ensure your external
/// event loop is never blocked but you would likely need to consider how
/// to throttle your own external loop.
///
/// Passing a `timeout` of `None` means that it may wait indefinitely for new
/// events before returning control back to the external loop.
///
/// **Note:** This is not a portable API, and its usage involves a number of
/// caveats and trade offs that should be considered before using this API!
///
/// You almost certainly shouldn't use this API, unless you absolutely know it's
/// the only practical option you have.
///
/// ## Synchronous events
///
/// Some events _must_ only be handled synchronously via the closure that
/// is passed to Winit so that the handler will also be synchronized with
/// the window system and operating system.
///
/// This is because some events are driven by a window system callback
/// where the window systems expects the application to have handled the
/// event before returning.
///
/// **These events can not be buffered and handled outside of the closure
/// passed to Winit.**
///
/// As a general rule it is not recommended to ever buffer events to handle
/// them outside of the closure passed to Winit since it's difficult to
/// provide guarantees about which events are safe to buffer across all
/// operating systems.
///
/// Notable events that will certainly create portability problems if
/// buffered and handled outside of Winit include:
/// - `RedrawRequested` events, used to schedule rendering.
///
/// macOS for example uses a `drawRect` callback to drive rendering
/// within applications and expects rendering to be finished before
/// the `drawRect` callback returns.
///
/// For portability it's strongly recommended that applications should
/// keep their rendering inside the closure provided to Winit.
/// - Any lifecycle events, such as `Suspended` / `Resumed`.
///
/// The handling of these events needs to be synchronized with the
/// operating system and it would never be appropriate to buffer a
/// notification that your application has been suspended or resumed and
/// then handled that later since there would always be a chance that
/// other lifecycle events occur while the event is buffered.
///
/// ## Supported Platforms
///
/// - Windows
/// - Linux
/// - MacOS
/// - Android
///
/// ## Unsupported Platforms
///
/// - **Web:** This API is fundamentally incompatible with the event-based way in which Web
/// browsers work because it's not possible to have a long-running external loop that would
/// block the browser and there is nothing that can be polled to ask for new new events.
/// Events are delivered via callbacks based on an event loop that is internal to the browser
/// itself.
/// - **iOS:** It's not possible to stop and start an `NSApplication` repeatedly on iOS so
/// there's no way to support the same approach to polling as on MacOS.
///
/// ## Platform-specific
///
/// - **Windows**: The implementation will use `PeekMessage` when checking for window messages
/// to avoid blocking your external event loop.
///
/// - **MacOS**: The implementation works in terms of stopping the global application whenever
/// the application `RunLoop` indicates that it is preparing to block and wait for new events.
///
/// This is very different to the polling APIs that are available on other
/// platforms (the lower level polling primitives on MacOS are private
/// implementation details for `NSApplication` which aren't accessible to
/// application developers)
///
/// It's likely this will be less efficient than polling on other OSs and
/// it also means the `NSApplication` is stopped while outside of the Winit
/// event loop - and that's observable (for example to crates like `rfd`)
/// because the `NSApplication` is global state.
///
/// If you render outside of Winit you are likely to see window resizing artifacts
/// since MacOS expects applications to render synchronously during any `drawRect`
/// callback.
fn pump_app_events<A: ApplicationHandler<Self::UserEvent>>(
&mut self,
timeout: Option<Duration>,
app: &mut A,
) -> PumpStatus {
#[allow(deprecated)]
self.pump_events(timeout, |event, event_loop| {
event_loop::dispatch_event_for_app(app, event_loop, event)
})
}
/// See [`pump_app_events`].
///
/// [`pump_app_events`]: Self::pump_app_events
#[deprecated = "use EventLoopExtPumpEvents::pump_app_events"]
fn pump_events<F>(&mut self, timeout: Option<Duration>, event_handler: F) -> PumpStatus
where
F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop);
}
impl<T> EventLoopExtPumpEvents for EventLoop<T> {
type UserEvent = T;
fn pump_events<F>(&mut self, timeout: Option<Duration>, event_handler: F) -> PumpStatus
where
F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop),
{
self.event_loop.pump_events(timeout, event_handler)
}
}
/// The return status for `pump_events`
pub enum PumpStatus {
/// Continue running external loop.
Continue,
/// Exit external loop.
Exit(i32),
}